adding all 'addon domains' under one ftp account

I am new to Ispconfig and I have just started to play around with the control panel and have managed to create a user. What I have not managed to figure out yet is how to add a ftp account for that user so that when he adds a new domain to his account he will be able to access all domains and upload and edit all his sites from one account.

I know this can be done with Cpanel with the 'add-on domains' but how can this be achieved with ispconfig 3 please?

What I wanted to do was to have one ftp account for all of the websites. The same as is done in Cpanel where there is one ftp account and whan the account user adds a addon domain/domains a folder/folders is created in that users ftp account so he can access the website/websites files from one ftp account. I will be adding alot of websites maybe 100 or 200 so that will mean making alot of FTP accounts if what I described above cannot be done from one ftp account.

If you would be able to access all sites from one FTP account, then a hacker that gets access to one of your sited e.g. when there is a vulnerability in one of the installed cms systems would be able to access all sites as well. This makes cpanel quite insecure. ISPConfig isolates each site by assigning a different Linux System user and group to the site and all php scripts run under this Linux system user and group. As a FTP user can only be assigned to one Linux System user, you can access only one site with a FTP user.

In ISPConfig 3.0.5 beta 1 there has been introduced a new feature that allows to add domains inside a existing site similar to what cpanel offers, but personally I wont use that on a server which runs websites that are connected to the internet due to the fact that a hack into one of these sites will affect all other sub sites as well.